So far, since the performance required for a bumper device for an automobile has been maintaining of a vehicle body at the time of a light collision (for example, 4 km/h pendulum impact test of U.S. PART 581), increasing the strength of the bumper device has been a main subject.
However, to comply with regulations such as one with respect to vehicle body damage at the time of 8 km/h pole, barrier collision test represented by the standard of U.S. Insurance Institute for Highway Safety (IIHS) or one with respect to passenger protection at the time of 55 km/h full lap collision test represented by the standard of JNCAP (Japan New Car Assessment Program), by having not only a strength but also an excellent crush (crush by applying pressure) property, an excellent material and structure is also required for energy absorption performance.
For this, the following countermeasures are employed. For example, a structure wherein a foamed material is filled in a bumper device (for example, JP-A-11-334500), a structure wherein an upper wall and a lower wall are formed to be inclined and these walls are structured to be able to buckled (for example, JP-A-2006-218904), a structure wherein a thickness of an intermediate rib is set to be larger than that of upper and lower ribs so that the formation of buckling or deformation becomes a specified formation (for example, JP-A-2004-148915), and a structure wherein a crush prevention body is disposed in a hollow portion of a bumper reinforcing material to be able to prevent sectional deformation and buckling and to give a rigidity (for example, JP-A-2000-52897), are known.
To adequately perform passenger protection at a time of being applied with a collision load, etc., required are to have adequate strength and rigidity capable of coping with a load being applied toward the passenger side and, in addition, to absorb an energy of the load being applied, by a bumper device itself as effectively as possible. In the above-described conventional structures, however, both of giving adequate strength and rigidity and giving excellent energy absorption performance are not always achieved.
Accordingly, it could be helpful to provide, in particular, a bumper device for an automobile which has desirable strength and rigidity while having a light-weight structure, and which can exhibit excellent energy absorption performance when a large load is inputted to a bumper beam.